The present invention relates to a device for automatically closing a door or window.
Conventional door closing devices have a spring hinge with one or two sleeves. Other types of automatic door closing devices have been developed, such as a floor hinge and a hydraulic damped hinge. However, they are complicated in structure and heavy in weight (for example, a floor hinge weighs 9-10 kilogrammes), and therefore are expensive.
The object of the present invention is to provide a new automatic door/window closing device which has a simple structure and light weight.
This object is accomplished according to the invention in a device having a center shaft provided with spiral channels on its surface and secured on the ground, steel balls rolling in the spiral channels, a floating piston which forms a screw pair with the center shaft by means of said steel balls, a housing with a flange which is to be secured to the door, a spring for supplying the force to automatically close the door, and a cover.
The spiral channel has a V-shaped section and two horizontal sections in both ends of the V-shaped section. When said steel balls are located in the V-shaped section of said channels, i.e. the door is opened to less than 90.degree. in either direction, the door will automatically close due to the force produced by said spring. When the door is not required to be closed, then the door is opened to 90.degree., the steel balls are located in the horizontal sections of said channels and self-locked, and the door stops moving for loss of the automatic closing function. When a period of time later, the opened door is to be closed, it only needs to be slightly pushed thereby causing the balls to slide out of the horizontal sections and into the V-shaped sections of said channels, so that the automatic door closing function returns.
Further features and advantages of the invention will become evident from the following claims, description and accomponying drawings.